提出了一种基于基元全息图频谱分析的计算全息参考光角度选择方法.通过分析基元全息图的空间频谱成分,导出全息图正确再现需要满足的约束条件;求解了基于空间光调制器的计算全息再现系统的参考光角度取值范围;用N-LUT算法计算了成像距离为1 000mm时,一幅22.5mm×26.1mm的二维图像取不同参考光角度时的全息图,并进行了数字再现和光学再现实验.结果表明:参考光角度在0.893 8°到1.398 0°之间选择可以获得质量良好的再现像;参考光角度小于0.893 8°时,再现像与共轭像不能完全分离,参考光角度大于1.398 0°时,全息图频率过高会造成欠采样,导致再现像与下一级共轭像互相交叠.实验现象与理论分析一致,验证了参考光夹角选择方法的正确性.
A method for choosing angle of reference beam in computer-generated holograms based on spatial frequency analysis of principle fringe pattern was proposed.The rules for reconstructed image rightly were obtained through analyzing the spatial frequency of principle fringe pattern.The angles of reference beam in the holography reconstructed system based on spatial light modulator were computed.The holograms of one image plane with size of 22.5 mm×26.1 mm were generated at the distance of1 000 mm when different angles of reference beam were chosen.The digital and optical reconstructed experiments were conducted respectively.The results indicate that the angle of reference beam must be chosen in the range which is from 0.893 8°to 1.398 0°in order to achieve good quality of reconstructed images.If the angle of reference beam is smaller than 0.893 8°,the reconstructed image and the conjugate image could not be separated completely,whereas the reconstructed image would overlap with the conjugate image of the next order if the angle of reference beam is larger than 1.398 0°.The experimental results validate the theoretical analysis very well.